U.S. patent application number 12/267607 was filed with the patent office on 2009-06-18 for high-friction fluid seal and shock absorber.
Invention is credited to Chikashi Imoto, Etsuro Nakada, Masatami Tsukamoto.
Application Number | 20090152779 12/267607 |
Document ID | / |
Family ID | 40638688 |
Filed Date | 2009-06-18 |
United States Patent
Application |
20090152779 |
Kind Code |
A1 |
Imoto; Chikashi ; et
al. |
June 18, 2009 |
High-Friction Fluid Seal and Shock Absorber
Abstract
A high-friction fluid seal used for high-friction sealing,
comprising a fluid seal lip provided on the working fluid filling
side to intercept a working fluid; and a dust lip provided on the
working fluid non-filling side (the outer side) of the fluid seal
lip to intercept dust coming from the outside, wherein the
thickness of a working fluid film formed on the extension stroke by
the dust lip is smaller than the thickness of a working fluid film
formed on the extension stroke by the fluid seal lip.
Inventors: |
Imoto; Chikashi; (Inuyama
City, JP) ; Tsukamoto; Masatami; (Kani City, JP)
; Nakada; Etsuro; (Kani City, JP) |
Correspondence
Address: |
Michael L. Crapenhoft;c/o Hiroe & Associates
4-3, Usa 3-chome
Gifu City
500-8368
omitted
|
Family ID: |
40638688 |
Appl. No.: |
12/267607 |
Filed: |
November 9, 2008 |
Current U.S.
Class: |
267/129 ;
277/558 |
Current CPC
Class: |
F16J 15/3232 20130101;
F16F 9/36 20130101; F16J 15/56 20130101; F16J 15/3244 20130101;
F16J 15/324 20130101 |
Class at
Publication: |
267/129 ;
277/558 |
International
Class: |
F16F 9/36 20060101
F16F009/36; F16J 15/32 20060101 F16J015/32 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 13, 2007 |
JP |
2007-294013 |
Claims
1. A high-friction fluid seal used for high-friction sealing,
comprising a fluid seal lip provided on the working fluid filling
side to intercept a working fluid; and a dust lip provided on the
working fluid non-filling side (the outer side) of the fluid seal
lip to intercept dust coming from the outside, wherein the
thickness of a working fluid film formed on the extension stroke by
the dust lip is smaller than the thickness of a working fluid film
formed on the extension stroke by the fluid seal lip.
2. The high-friction fluid seal according to claim 1, wherein by
making a maximum surface pressure inclination on the fluid seal lip
side of the dust lip larger than a maximum surface pressure
inclination on the working fluid filling side of the fluid seal
lip, the thickness of the working fluid film formed on the
extension stroke by the dust lip is made smaller than the thickness
of the working fluid film formed on the extension stroke by the
fluid seal lip.
3. The high-friction fluid seal according to claim 1, wherein by
making an angle between an inclined face on the fluid seal lip side
of the dust lip and a contact surface with which the fluid seal lip
is in contact larger than an angle between an inclined face on the
working fluid filling side of the fluid seal lip and the contact
surface, the thickness of the working fluid film formed on the
extension stroke by the dust lip is made smaller than the thickness
of the working fluid film formed on the extension stroke by the
fluid seal lip.
4. The high-friction fluid seal according to claim 1, wherein a
highly inclined face is provided on the inside of the tip end of
the dust lip, and an angle between the highly inclined face and the
contact surface is made larger than an angle between a general
inclined face on the inside of the dust lip and the contact
surface, whereby the thickness of the working fluid film formed on
the extension stroke by the dust lip is made smaller than the
thickness of the working fluid film formed on the extension stroke
by the fluid seal lip.
5. A cylinder-type shock absorber using a working fluid, wherein
the high-friction fluid seal described in claim 1 is used as a seal
between a piston rod and a cylinder body.
6. A cylinder-type shock absorber using a working fluid, wherein
the high-friction fluid seal described in claim 2 is used as a seal
between a piston rod and a cylinder body.
7. A cylinder-type shock absorber using a working fluid, wherein
the high-friction fluid seal described in claim 3 is used as a seal
between a piston rod and a cylinder body.
8. A cylinder-type shock absorber using a working fluid, wherein
the high-friction fluid seal described in claim 4 is used as a seal
between a piston rod and a cylinder body.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a high-friction fluid seal
used for high-friction sealing which includes a fluid seal lip
provided on the working fluid filling side to intercept a working
fluid and a dust lip provided on the working fluid non-filling side
(the outer side) of the fluid seal lip to intercept dust coming
from the outside.
[0002] Also, the present invention relates to a cylinder-type shock
absorber using a working fluid, which uses the aforementioned
high-friction fluid seal as a seal between a piston rod and a
cylinder body.
[0003] Shock absorbers, which are usually of a cylinder type, play
a role in buffering external force by regulating the flow rate of a
working fluid moving in the shock absorber, and are used for a
suspension of a vehicle, an opening and closing part of a rear door
of a vehicle, and the like.
[0004] The shock absorber described in Japanese Unexamined Patent
Application Publication No. 2006-17161, which is one of the type of
shock absorbers described above, is used for a vehicular
suspension. In the sealing structure of the shock absorber,
deformation preventing means (9b, 9c) (here, reference characters
used in Japanese Unexamined Patent Application Publication No.
2006-17161 are shown in parentheses) are provided on an inclined
face (9a) for lip storage of a rod guide (5) on the cylinder side
with which the inner surface of an outer peripheral lip (18) of an
oil seal (6) is in contact, by which seal failure caused by
assembling work can be prevented.
[0005] The oil seal (6) used in this shock absorber has the same
basic configuration as that of the high-friction fluid seal in
accordance with the present invention. The oil seal (6) includes an
oil lip (15) for intercepting working fluid ("working oil" in
Japanese Unexamined Patent Application Publication No. 2006-17161),
which is provided on the working fluid filling side, and a dust lip
(14) for sealing dust coming from the outside, which is provided on
the working fluid non-filling side (the outer side) of the oil seal
(15).
[0006] Usually, a shock absorber used for a suspension is provided
so that the tip end of the rod (4) is on the upside, and is
configured so that the dust lip (14) thereof prevents dust
(including rainwater and sometimes oil, etc. mixed in a puddle)
coming from the outside from entering therein.
[0007] The dust lip (14) configured as described above cannot
prevent oil film formed on the extension stroke of the oil lip
(15), which comes inversely from the inside, from leaking out.
[0008] On the other hand, the shock absorber used for a suspension
has a problem in that it is difficult to obtain a damping force at
very low speeds and very small vibrations by the buffering action
of working fluid. Therefore, in recent years, a high-friction fluid
seal for high-friction sealing has been proposed which can obtain a
damping force at very low speeds and very small vibrations by a
frictional force between the fluid lip of fluid seal and a piston
rod.
[0009] In this case, as a method for high-friction sealing, there
are a method in which the friction coefficients of the working
fluid and the material of the fluid seal are increased and a method
in which the tightening force of the fluid seal on the piston rod
(surface pressure of contact surface between both of the elements)
is increased.
[0010] However, in both methods, a working fluid film formed on the
contact surface between the fluid lip of the high-friction fluid
seal and the piston rod is pushed out in the state in which the
shock absorber is not operated for a long period of time (for
example, parking time), so that the working fluid film may
break.
[0011] Also, in the fluid seal for high-friction sealing, a slide
of the contact surface, that is, the sliding contact between the
fluid lip and the piston rod is restrained to a high degree.
[0012] Therefore, for these reasons, if the shock absorber using
the high-friction fluid seal is left in an inoperative state for a
long period of time, the fluid lip and the piston rod stick
together. If the shock absorber is operated (the vehicle or the
like is operated) in this state, a gap (opening) is formed in a
part of the circumference of the contact surface between the fluid
lip and the piston rod, and therefore the working fluid may leak
out.
[0013] The working fluid leaking out of the fluid lip remains once
in a fluid reservoir, which is a space between the fluid lip and
the dust lip. However, since the dust lip does not prevent the
working fluid from leaking from the inside of the dust lip to the
outside thereof as described above, the working fluid leaking out
of the fluid lip passes through the dust lip and is gradually
discharged to the outer side (the atmosphere side), this state
being judged to be working fluid leakage (oil leakage).
[0014] The working fluid leakage of this type occurs only when the
vehicle is moved suddenly after being left for a long period of
time, and the amount of leaking working fluid is also small.
Therefore, this leakage differs from progressive leakage such that
a flaw is induced at the outer periphery of the piston rod,
resulting in leakage. However, this leakage gives a sense of unease
to the user of vehicle, so that improvement has been demanded.
[0015] FIGS. 7(a)-7(c) show a background art of the present
invention, showing a gas spring using a seal capable of preventing
this leakage of working fluid. FIG. 7(a) is a longitudinal
sectional view of the gas spring, FIG. 7(b) is an enlarged
sectional view of a part of a seal, and FIG. 7(c) is a partially
enlarged sectional view of FIG. 7(b). This gas spring (shock
absorber) is one described in Japanese unexamined Patent
Application Publication No. 2002-286067.
[0016] This gas spring 50 includes a seal 40 having the
above-described features, and also includes a cylinder body 41, a
body-side connecting part 41a, a piston 42, a piston rod 43, a
rod-side connecting part 43a, a bearing 44, and a retainer 45 as
the basic components of a shock absorber.
[0017] The interior of the cylinder body 41 is divided into a gas
chamber A and a fluid chamber L by the piston 42. The piston 42 is
provided with a port 42a, by which high-pressure gas in the gas
chamber A can flow between the gas chamber A and the fluid chamber
L.
[0018] By the above-described configuration, the gas spring 50
always urges a rear door in the opening direction and gives a
proper damping force to the opening/closing movement of the rear
door by means of the pressure of the high-pressure gas in the gas
chamber A in a posture shown in FIG. 7(a), that is, in the state in
which the body-side connecting part 41a is connected to the upper
side (the rear door side) and the rod-side connecting part 43a is
connected to the lower side (the vehicle body side).
[0019] The seal 40, which is a feature of the gas spring 50,
includes a sub lip 31, a main lip 32, an insert metal 33, and an
outer peripheral lip 34 as shown in FIG. 7(b). A fluid reservoir
S', which is a space between the sub lip 31 and the main lip 32, is
made a large space, as compared with the conventional gas spring,
by providing the main lip 32 on the inside (the fluid chamber L
side) of the insert metal 33 and the sub lip 31 on the outside
thereof.
[0020] Also, as shown in FIG. 7(c), the lip tip end of the sub lip
31 is formed into a substantially trapezoidal shape. Specifically,
the lip tip end of the sub lip 31 has an upper face a, a side face
b, and a bottom face c, and an angle .theta.1 between the upper
face a and the piston rod 43 is formed so as to be larger than an
angle .theta.2 between the side face b and the piston rod 43.
Thereby, the working fluid is prevented from leaking in such a
manner that the lip tip end always scrapingly returns the working
fluid in the fluid reservoir S' in the direction toward the fluid
reservoir S' (paragraph [0030] of Japanese Unexamined Patent
Application Publication No. 2002-286067).
[0021] By the above-described configuration, according to this gas
spring 50, the working fluid can be prevented from leaking out of
the sub lip 31. Also, in the case where the gas spring 50 is used
in a posture such that the sub lip 31 is on the downside, a problem
in that dust, water, and the like intrude from the outside is less
liable to occur.
[0022] However, in the case where the gas spring 50 is used in a
reverse posture as the shock absorber for vehicular suspension as
described in Japanese Unexamined Patent Application Publication No.
2006-17161, that is, it is used in a posture such that the sub lip
31 is on the upside, the sub lip 31 cannot perform function as a
dust lip, that is, cannot prevent dust and water coming from the
upper outside from intruding. Therefore, the seal 40 of such a gas
spring 50 cannot be used as a shock absorber for suspension.
Japanese Unexamined Patent Application Publication No. 2006-17161
discloses a coarse face 9b serving as a deformation preventing
means shown in FIGS. 1 and 3, and a protrusion 9c serving as a
deformation preventing means shown in FIG. 4. Japanese Unexamined
Patent Application Publication No. 2002-286067 discloses a seal 19
shown in FIGS. 1 to 3, and a sub lip 23 thereof.
SUMMARY OF THE INVENTION
[0023] The present invention has been made to solve the above
problems, and accordingly an object thereof is to provide a
high-friction fluid seal capable of solving a problem of working
fluid leakage from a fluid lip while providing a dust lip capable
of being used for a shock absorber for a suspension of a vehicle or
the like, and a shock absorber provided with the aforementioned
high-friction fluid seal.
[0024] A high-friction fluid seal of this invention is used for
high-friction sealing, comprising a fluid seal lip provided on the
working fluid filling side to intercept a working fluid, and a dust
lip provided on the working fluid non-filling side (the outer side)
of the fluid seal lip to intercept dust coming from the outside,
wherein the thickness of a working fluid film formed on the
extension stroke by the dust lip is made smaller than the thickness
of a working fluid film formed on the extension stroke by the fluid
seal lip.
[0025] In a cylinder-type shock absorber using a working fluid of
this invention, the high-friction fluid seal described of this
invention is used as a seal between a piston rod and a cylinder
body.
[0026] In the high-friction fluid seal of this invention, because
the thickness of a working fluid film formed on the extension
stroke by the dust lip is made smaller than the thickness of a
working fluid film formed on the extension stroke by the fluid seal
lip, the problem of working fluid leakage from a fluid lip is
solved, while providing a dust lip capable of being used for a
shock absorber for a suspension of a vehicle or the like.
[0027] The cylinder-type shock absorber using a working fluid of
this invention, wherein the high-friction fluid seal described of
this invention is used as a seal between a piston rod and a
cylinder body, can provide that effect of the high-friction fluid
seal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1(a) is a sectional view showing an upper half of one
example of a fluid seal having a basic configuration, which is the
basis of a high-friction fluid seal in accordance with the present
invention, FIG. 1(b) is Equation 1 used for explaining the basic
principle of FIG. 1(a), FIG. 1(c) is an explanatory view showing an
inclined face of a fluid lip in the service state of FIG. 1(a) and
the relationship between surface pressure distribution and maximum
surface pressure inclination, FIG. 1(d) is an enlarged sectional
view of a dust lip, and FIG. 1(e) is an explanatory view showing an
inclined face of a dust lip in the service state of FIG. 1(a) and
the relationship between surface pressure distribution and maximum
surface pressure inclination;
[0029] FIG. 2 is a sectional view showing one example of a
high-friction fluid seal in accordance with the present
invention;
[0030] FIG. 3(a) is a sectional view showing an upper half of
another example of a high-friction fluid seal in accordance with
the present invention, FIG. 3(b) is an enlarged sectional view of a
dust lip of FIG. 3(a), FIG. 3(c) is a service state view of FIG.
3(b), and FIG. 3(d) is an explanatory view showing an inclined face
of the dust lip shown in FIG. 3(b) and the relationship between
surface pressure distribution and maximum surface pressure
inclination;
[0031] FIGS. 4(a), 4(b) and 4(c) are sectional views showing dust
lip parts of other examples of a high-friction fluid seal in
accordance with the present invention;
[0032] FIGS. 5(a) and 5(b) are enlarged sectional views showing tip
end parts of dust lips of other examples of a high-friction fluid
seal in accordance with the present invention;
[0033] FIG. 6 is a longitudinal sectional view showing one example
of a shock absorber using the high-friction fluid seal shown in
FIG. 3(a); and
[0034] FIGS. 7(a)-7(c) are views showing a gas spring using a seal
that is a background art of the present invention, FIG. 7(a) being
a longitudinal sectional view of the gas spring, FIG. 7(b) being an
enlarged sectional view of a part of the seal, and FIG. 7(c) being
a partially enlarged sectional view of FIG. 7(b).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] The basic concept and embodiment of the present invention
will now be described with reference to the accompanying
drawings.
<Basic Principle of Fluid Seal and Basic Concept of the Present
Invention>
[0036] FIG. 1(a) is a sectional view showing an upper half of one
example of a fluid seal having a basic configuration, which is the
basis of a high-friction fluid seal in accordance with the present
invention, FIG. 1(b) is Equation 1 used for explaining the basic
principle of FIG. 1(a), FIG. 1(c) is an explanatory view showing an
inclined face of a fluid lip in the service state of FIG. 1(a) and
the relationship between surface pressure distribution and maximum
surface pressure inclination, FIG. 1(d) is an enlarged sectional
view of a dust lip in FIG. 1(a), and FIG. 1(e) is an explanatory
view showing an inclined face of a dust lip in the service state of
FIG. 1(c) and the relationship between surface pressure
distribution and maximum surface pressure inclination.
[0037] First, the basic principle of the fluid seal, which is the
basis of the invention concept of a high-friction fluid seal in
accordance with the present invention, is explained with reference
to FIG. 1.
[0038] The fluid seal 30 shown in FIG. 1(a), which is used for a
shock absorber for a suspension of a vehicle or the like, includes
a dust lip 21 for preventing dust (including rainwater and
sometimes oil, etc. mixed in a puddle) coming from the outside from
intruding, a fluid seal lip 22 provided on the working fluid side
of the dust lip 21 to prevent the working fluid on the inside from
leaking, an insert metal 23 for supporting these lips 21 and 22,
and an outer peripheral lip 24 provided on the outer periphery side
of the insert metal 23.
[0039] On the outer periphery side of the fluid seal lip 22, a
garter spring 25 is provided to adjust the tightening force of the
fluid seal lip 22 on a piston rod 13 (indicated by an imaginary
line of two-dot chain line in FIG. 1(a), refer to FIG. 6). Also, at
an intermediate position in the radial direction between the outer
peripheral lip 24 and the fluid seal lip 22 on the working fluid
filling-side surface of the insert metal 23, an auxiliary lip 26 is
provided so as to be in contact with the upper surface of a
connecting part 15c (refer to FIG. 6) on the shock absorber side
and be bent.
[0040] As shown in FIG. 1(a), the inclined face on the working
fluid side of the fluid seal lip 22 is called a fluid seal lip
fluid-side inclined face 22a, the inclined face on the dust lip 21
side thereof is called a fluid seal lip dust-side inclined face
22b, the inclined face on the fluid seal lip 22 (working fluid)
side of the dust lip 21 is called a dust lip fluid-side inclined
face 21a, and the inclined face on the working fluid non-filling
side thereof is called a dust lip outer-side inclined face 21b.
[0041] An inclined part continuous with the dust-side inclined face
21b of the dust lip 21 is called an upper inclined part 21d, and a
part in which the upper inclined part 21d is fixed to the outer
side surface of the insert metal 23 is called a fixing part 21e. A
symbol M denotes the axis centerline of a high-friction fluid seal
10.
[0042] Also, the angles between the fluid seal lip fluid-side
inclined face 22a, the fluid seal lip dust-side inclined face 22b,
the dust lip fluid-side inclined face 21a, and the dust lip
outer-side inclined face 21b and the contact surface of the piston
rod 13 to be sealed by these lips 22 and 21 (the rod axis center)
are called a fluid seal lip fluid-side inclination angle .alpha.1,
a fluid seal lip dust-side inclination angle .alpha.2, a dust lip
fluid-side inclination angle .alpha.3, and a dust lip outer-side
inclination angle .alpha.4, respectively.
[0043] Also, a space formed between the fluid seal lip 22 and the
dust lip 21 so as to face to the piston rod 13 to be mounted is
called a fluid reservoir S.
[0044] The following relationships hold between the above-described
inclination angles .alpha.1 to .alpha.4.
[0045] Relationship 1: a relationship such that the fluid seal lip
fluid-side inclination angle .alpha.1 is larger than the fluid seal
lip dust-side inclination angle .alpha.2. Relationship 2: a
relationship such that the dust lip outer-side inclination angle
.alpha.4 is larger than the dust lip fluid-side inclination angle
.alpha.3. The reason why the relationships 1 and 2 hold is
explained.
[0046] FIG. 1(c) shows a service state of the fluid seal lip 22,
that is, an enlarged view of a state in which the fluid seal lip 22
is mounted on the piston rod 13 of the shock absorber, and a
surface pressure distribution MB1 on the contact surface between
the fluid seal lip 22 and the piston rod 13.
[0047] As shown in FIG. 1(c), the surface pressure distribution MB1
takes a mountain shape, and the maximum surface pressure
inclination lies on both sides of the mountain peak. The film
thickness h of the working fluid is always determined by the
surface pressure inclination on the side on which the working fluid
is drawn. Therefore, if the case where the seal 30 is fixed and the
piston rod 13 moves to the right direction (the working fluid
non-filling direction) is taken as an extension stroke, a
fluid-side extension stroke fluid film thickness h1 on the
extension stroke is determined by a fluid seal lip fluid-side
maximum surface pressure inclination .theta.1 on the left-hand side
of the peak of surface pressure, and a fluid-side compression
stroke fluid film thickness h2 on the compression stroke is
determined by a fluid seal lip fluid-side inclined face angle
.theta.2 on the right-hand side of the peak of surface
pressure.
[0048] The mechanism of the working fluid flow of the fluid seal
lip 22 can be explained as described below.
[0049] (1) Leakage means a state in which a scraped-out fluid film
is deposited by repeated operation in the case where the fluid-side
extension stroke fluid film thickness h1 formed on the extension
stroke is larger than the fluid-side compression stroke fluid film
thickness h2 formed on the compression stroke.
[0050] The fluid-side extension stroke fluid film thickness h1
formed on the extension stroke is the thickness of a working fluid
film formed on the outer peripheral surface of the piston rod 13
after the lip 22 has passed through the piston rod 13, so that it
is also called a formed film thickness h1.
[0051] Also, the fluid-side compression stroke fluid film thickness
h2 formed on the compression stroke means a film thickness capable
of taking in the working fluid film formed on the outer peripheral
surface of the piston rod 13 to the working fluid filling side, so
that it is also called a taking-in film thickness h2.
[0052] (2) Therefore, to prevent the working fluid leakage, the
fluid-side extension stroke fluid film thickness (formed film
thickness) h1 formed on the extension stroke must be made smaller
than or at least almost equal to the fluid-side compression stroke
fluid film thickness (taking-in film thickness) h2 formed on the
compression stroke.
[0053] (3) The fluid film thickness is determined by Equation 1
shown in FIG. 1(b). In Equation 1, h is fluid film thickness, .mu.
is working fluid viscosity, and V is velocity on the contact
surface of the lip (in this example, on the piston rod).
[0054] The condition that fluid leakage does not occur is to make
the formed film thickness h1 on the extension stroke not larger
than the taking-in film thickness h2 on the compression stroke,
and, as for the surface pressure inclination, to set the maximum
surface pressure inclination .theta.1 on the extension stroke so as
to be larger than the maximum surface pressure inclination .theta.2
on the compression stroke.
[0055] A simple setting method is as shown in FIG. 1(c). The fluid
seal lip 22 has a triangular cross section in a non-service state,
and the left-hand side thereof is the working fluid filling side,
and the right-hand side thereof is the working fluid non-filling
side (outer side). It is assumed that the working fluid leakage
from the left-hand side to the right-hand side is prevented.
[0056] When it is assumed that the angle that the inclined face 22a
on the left-hand side of the lip 22 makes with the axis line of the
rod, that is, the contact surface of the lip 22 is taken as a fluid
seal lip fluid-side inclination angle .alpha.1, the angle that the
inclined face 22b on the right-hand side thereof makes with the
axis line of the rod, that is, the contact surface of the lip 22 is
taken as a fluid seal lip dust-side inclination angle .alpha.2, and
.alpha.1 is larger than .alpha.2, the inclined faces in a service
state become inclined faces 22a' and 22b' (hereinafter, for the
inclined face in a service state with respect to the inclined face
in a non-service state, ['] is added to the symbol), and the
occurring surface pressure distribution MB1 becomes as shown in
FIG. 1(c), having an asymmetrical shape in which the peak of
surface pressure deviates to the left-hand side (the working fluid
filling side).
[0057] The maximum surface pressure inclination .theta.1 on the
left-hand side becomes larger than the maximum surface pressure
inclination .theta.2 on the right-hand side, by which leakage can
be prevented. This is the reason why relationship 1 is made hold
generally for a fluid. seal lip 22 of the fluid seal 30.
[0058] This principle is applied to the dust lip 21 in FIGS. 1(d)
and 1(e). In the dust lip 21, the dust lip outer-side inclination
angle .alpha.4 is larger than the dust lip fluid-side inclination
angle .alpha.3. As a result, as shown in FIG. 1(e), a surface
pressure distribution MB2 takes a mountain shape in which the peak
of surface pressure deviates to the right-hand side (the outer
side), and a dust lip outer-side maximum surface pressure
inclination .theta.4 is larger than a dust lip fluid-side maximum
surface pressure inclination .theta.3.
[0059] As a result, in the dust lip 21, a dust-side compression
stroke fluid film thickness (taking-in film thickness) h4 is
smaller than a dust-side extension stroke fluid film thickness
(formed film thickness) h3, by which dust is prevented from
intruding from the outside. This is the reason why relationship 2
is made hold generally for a fluid dust lip 1 of the fluid seal
30.
[0060] However, in the case where the high-friction fluid seal 10
provided with such a dust lip 1 is used as an oil seal for
high-friction sealing of a suspension of a vehicle or the like,
attention is not given to the relationship between the formed film
thickness h3 and the formed film thickness h1 of the fluid seal lip
22 as shown by the fluid seal 30 having the basic configuration,
and in the case where the formed film thickness h3 is larger than
the formed film thickness h1 (usually, the formed film thickness h3
is larger than the formed film thickness h1 to increase the effect
of the dust lip 21), the working fluid film leaking from the fluid
seal lip 22 side is made pass through after the shock absorber has
been left for a long period of time.
[0061] The shapes of the inclined faces 21a and 21b of such a dust
lip 21 are fit for the purpose of preventing dust (including
rainwater and sometimes oil, etc. mixed in a puddle) from intruding
from the outside. However, in the case where the dust lip is used
for high-friction sealing, the above-described drawbacks occur.
[0062] Thereupon, the applicant of the present invention paid
attention to the relationship between the fluid-side extension
stroke fluid film thickness h1 and the dust-side extension stroke
fluid film thickness h3, which relationship has not attracted
attention conventionally, and hit upon an idea that while the basic
properties of the fluid seal lip and the dust lip are maintained,
that is, a condition that for the fluid seal lip, the fluid-side
compression stroke fluid film thickness h2 is made larger than the
fluid-side extension stroke fluid film thickness h1, and for the
dust lip, the dust-side extension stroke fluid film thickness h3 is
made larger than the dust-side compression stroke fluid film
thickness h4 is maintained, first, the dust-side extension stroke
fluid film thickness h3 is made smaller than the fluid-side
extension stroke fluid film thickness h1.
[0063] In this case, even if a fluid film of the fluid-side
extension stroke fluid film thickness h1 is formed in the fluid
seal lip on the extension stroke while the basic properties of
these lips are maintained, of the fluid films, in the dust lip,
only the fluid film of the dust-side extension stroke fluid film
thickness h3 is allowed to be formed. If the dust-side extension
stroke fluid film thickness h3 is made sufficiently small, the
fluid film h3 formed on the piston rod on the outer side of the
dust lip evaporates or gets scattered before depositing, so that
the fluid film h3 can be made incapable of being recognized by the
user.
[0064] That is to say, according to the high-friction fluid seal in
which the dust-side extension stroke fluid film thickness h3 is
made smaller than the fluid-side extension stroke fluid film
thickness h1 (a first invention), the problem of working fluid
leakage from the fluid seal lip can be solved while the dust lip
capable of being used for a shock absorber for a suspension of a
vehicle or the like is provided.
[0065] Although regarding the fluid seal provided with the fluid
seal lip for intercepting a fluid and the dust lip for keeping out
dust, attention has been given to the individual lip so that the
lip fulfils the respective purpose, the first invention arrived at
this high-friction fluid seal that functions as high-friction seal
by cooperation of both of the lips, that is, serves as a seal
system in which both of the lips are combined by hitting an idea
that the dust lip is also anticipated newly in intercepting the
working fluid.
[0066] Also, the first invention results in a fact that other
conditions, for example, the tightening allowance on the piston rod
forming the contact surface with which the fluid seal lip and the
dust lip are in contact, are made appropriate, the above-described
film thickness principle can be applied commonly to both of the
lips, and as a result, the dust lip fluid-side maximum surface
pressure inclination is made larger than the fluid seal lip
fluid-side maximum surface pressure inclination (a second
invention), and the effect thereof is also the same as described
above.
[0067] Further, the first invention results in a fact that assuming
that the same other conditions are met, in the service state, the
dust lip fluid-side inclined face angle is made larger than the
fluid seal lip fluid-side inclined face angle (a third invention),
and the effect thereof is also the same as described above.
First Embodiment
[0068] FIG. 2 is a sectional view showing one example of the
high-friction fluid seal in accordance with the present
invention.
[0069] This high-friction fluid seal 10 embodies the third
invention of the basic concept of the present invention, and like
the high-friction fluid seal 10 shown in FIGS. 1(a)-1(e), is used
for a shock absorber 20 used for a suspension of a vehicle or the
like.
[0070] The high-friction fluid seal 10, which is used as a
high-friction seal in industrial application fields like the fluid
seal 30 shown in FIGS. 1(a)-1(e), includes, as basic components, a
dust lip 21, a fluid seal lip 2, an insert metal 3, an outer
peripheral lip 4, a garter spring 5, and an auxiliary lip 6
corresponding to the dust lip 21, the fluid seal lip 22, the insert
metal 23, the outer peripheral lip 24, the garter spring 25, and
the auxiliary lip 26 of the fluid seal 30, respectively.
[0071] The high-friction fluid seal 10 further includes an upper
inclined part 1d and a fixing part 1e corresponding to the upper
inclined part 21d and a fixing part 21e of the fluid seal 30 shown
in FIGS. 1(a)-1(e), respectively. A symbol M denotes the axis
centerline of the high-friction fluid seal 10, and after the
high-friction fluid seal 10 has been mounted to the shock absorber
30, the axis centerline M coincides with the axis center line of
the piston rod 13 of the shock absorber 20.
[0072] Like the inclined faces of the lips 1 and 2, the inclined
face on the fluid seal lip 2 side of the dust lip 1 is called a
dust lip fluid-side inclined face 1a, the inclined face on the
working fluid non-filling side thereof is called a dust lip
outer-side inclined face 1b, the inclined face on the working fluid
side of the fluid seal lip 2 is called a fluid seal lip fluid-side
inclined face 2a, and the inclined face on the dust lip 1 side
thereof is called a fluid seal lip dust-side inclined face 2b.
[0073] Also, like the angles of the inclined faces of the lips 21
and 22, the angles between the fluid seal lip fluid-side inclined
face 2a, the fluid seal lip dust-side inclined face 2b, the dust
lip fluid-side inclined face 1a, and the dust lip outer-side
inclined face 1b and the contact surface of the piston rod 13 to be
sealed by these lips 2 and 1 are called a fluid seal lip fluid-side
inclination angle .beta.1, a fluid seal lip dust-side inclination
angle .beta.2, a dust lip fluid-side inclination angle .beta.3, and
a dust lip outer-side inclination angle .beta.4, respectively.
[0074] This high-friction fluid seal 10 differs from the fluid seal
30 shown in FIGS. 3(a)-3(d) in that the dust lip fluid-side
inclination angle .beta.3 is larger than the fluid seal lip
fluid-side inclination angle .beta.1.
[0075] Also, corresponding to the above-described fact, the dust
lip 1 has a triangular shape that is similar to the shape of the
fluid seal lip 2, the triangular shape extending almost directly
below from the outer side of the insert metal 3 toward the piston
rod 13, so that the length exerting an influence on the rigidity
and flexibility of the dust lip 1 is short.
[0076] In this case, the dust lip fluid-side inclined face angle is
larger than the fluid seal lip fluid-side inclined face angle in
the service state, so that the effect of the third invention of the
basic concept can be achieved more specifically. Also, this fact
means that the effects of the second and first inventions can also
be achieved.
[0077] Since the dust lip 1 has a short length, the high-friction
fluid seal 10 can be applied to a case where vibrations in the
radial direction, that is, transverse vibrations of the piston rod
of the shock absorber are small. Also, since the dust lip
outer-side inclination angle .beta.4 cannot be made too large, the
high-friction fluid seal 10 can be applied to industrial fields in
which the dust seal effect is not demanded so much as compared with
the ordinary case.
Second Embodiment
[0078] FIG. 3(a) is a sectional view showing an upper half of
another example of the high-friction fluid seal in accordance with
the present invention, FIG. 3(b) is an enlarged sectional view of a
dust lip of FIG. 3(a), FIG. 3(c) is a service state view of FIG.
3(b), and FIG. 3(d) is an explanatory view showing an inclined face
of the dust lip shown in FIG. 3(b) and the relationship between
surface pressure distribution and surface pressure inclination. In
FIGS. 3(a)-3(d), the same symbols are applied to elements that have
already been explained, and the explanation of these elements is
omitted.
[0079] This high-friction fluid seal 10A differs from the
high-friction fluid seal 10 shown in FIG. 2 in that the entire
shape of a dust lip 1A is common to the dust lip 21 of the fluid
seal 30 shown in FIGS. 1(a)-1(e).
[0080] In addition, the dust lip 1A is provided with highly
inclined face 1c on the inside at the tip end thereof. As shown in
FIG. 3(a), highly inclined face angle .beta.7 between the highly
inclined face 1c and the contact surface (the piston rod 13) is
larger than an angle .beta.5 between a general inclined face 1f on
the inside of the dust lip 1A and the contact surface, and thereby
is made larger than the fluid-side inclination angle .beta.1 of the
fluid seal lip 2. Thereby, the working fluid film thickness h3
formed on the extension stroke of the dust lip 1A is made smaller
than the working fluid film thickness h1 formed on the extension
stroke of the fluid seal lip 2.
[0081] The high-friction fluid seal 10A is common to the
high-friction fluid seal 10 shown in FIG. 2 except the
above-described features, and the basic shape of the dust lip 1A
differs from the tip end part shape of the relating dust lip 1A
because the highly inclined face 1c is provided.
[0082] That is to say, the dust lip 1A of the high-friction fluid
seal 10A includes a dust lip fluid-side inclined face 1a, a dust
lip outer-side inclined face 1g, an upper inclined part 1h, and a
fixing part 1e, that are the same as the dust lip fluid-side
inclined face 21a, the dust lip outer-side inclined face 21b, the
upper inclined part 21d, and the fixing part 21e, respectively,
that the dust lip 21 of the fluid seal 30 shown in FIGS. 1(a)-1(e)
includes.
[0083] The tip end part of the dust lip fluid-side inclined face 1a
is continuous with the highly inclined face 1c via an inflection
point. The highly inclined face 1c is continuous with the dust lip
outer-side inclined face 1g while forming a projecting part 1t
having a rounded cross section in the tip end part of the dust lip
1A.
[0084] The projecting part 1t having a rounded cross section that
connects the inclined face 1c and the dust lip outer-side inclined
face 1g to each other is a part corresponding to a part in which
the fluid-side inclined face 21a and the dust lip outer-side
inclined face 21b of the dust lip 1 of the fluid seal 30 shown in
FIG. 1 are connected to each other. In the dust lip 1A, the
projecting part 1t is a projecting part formed resultantly to
provide the highly inclined face 1c in the tip end part of the dust
lip fluid-side inclined face 1f.
[0085] The angles between the dust lip fluid-side inclined face 1a,
the dust lip outer-side inclined face 1g, and the highly inclined
face 1c and the contact surface (rod axis center) of the piston rod
13 to be sealed are called the dust lip fluid-side inclination
angle .beta.5, a dust lip out-side inclination angle .beta.6, and
the highly inclined face angle .beta.7, respectively.
[0086] As seen from FIG. 3(a), the relationship between the
inclination angles in the non-service state of the high-friction
fluid seal 10A is a relationship such that the dust seal lip
fluid-side inclination angle .beta.5 is smaller than the fluid seal
lip fluid-side inclination angle .beta.1, but the highly inclined
face angle .beta.7 is larger than the fluid seal lip fluid-side
inclination angle .beta.1.
[0087] Also, to perform the respective basic function of the fluid
seal lip 2 and the dust lip 1A, the fluid seal lip fluid-side
inclination angle .beta.1 is made larger than the fluid seal lip
dust-side inclination angle .beta.2, and the highly inclined face
angle .beta.7 is made smaller than the dust lip outer-side
inclination angle .beta.6.
[0088] When the high-friction fluid seal 10A configured as
described above is mounted on the shock absorber 20, the dust lip
1A is deformed as shown in FIG. 3(c). FIG. 3(d) is an enlarged
sectional view of a contact part between the deformed dust lip 1A
and the piston rod 13, additionally showing a surface pressure
distribution.
[0089] Also, as compared with the dust lip 21 of the fluid seal 30
shown in FIG. 1, only the projecting part 1t that is shorter in the
axial direction of the piston rod 13 comes into contact with the
rod 13 and is deformed, and the dust lip fluid-side inclined face
1f continuous with the highly inclined face 1c forming the
projecting part 1t does not come into contact with the rod 13.
Therefore, the dust lip 1A comes into contact with the piston rod
13 in a contact part that is shorter in the axial direction, and
therefore only the projecting part 1t of the dust lip 1A takes part
in the surface pressure distribution, so that a surface pressure
distribution MB3 as shown in FIG. 3(d) is formed.
[0090] Resultantly, a result is obtained that a dust lip fluid-side
maximum surface pressure inclination .theta.7 becomes remarkably
larger than the fluid seal lip fluid-side maximum surface pressure
inclination .theta.1, and thereby the dust-side extension stroke
fluid film thickness h3 is made an order of magnitude smaller than
the fluid-side extension stroke fluid film thickness h1.
[0091] Also, it is proved that the surface pressure distribution
MB3 takes a mountain shape deviating as a whole to the right-hand
side (the outer side) in FIGS. 1(a)-1(e) though slightly, and a
dust lip outer-side maximum surface pressure inclination .theta.6
is larger than the dust lip fluid-side maximum surface pressure
inclination .theta.7, so that a function as a dust lip is also
fulfilled.
[0092] Therefore, according to this high-friction fluid seal 10A,
the effects of the above-described first invention, second
invention, and third invention can be achieved.
[0093] Also, the shape of the dust lip 1A is almost the same as the
shape of the dust lip 21 of the fluid seal 30 shown in FIGS.
1(a)-1(e) except the highly inclined face 1c part, so that similar
strength against transverse amplitude can be achieved.
[0094] Since the dust lip is made of a viscoelastic material such
as rubber, a permanent set phenomenon occurs intrinsically in a
long term. If permanent set occurs in the tip end part of the dust
lip, both of the surface pressure and the surface pressure
inclination decrease with respect to the initial values, so that
the fluid film thickness also increases.
[0095] However, in the case of the present invention, since the
dust lip 1A comes into contact with the piston rod 13 by the
projecting part 1t only, the original value of surface pressure
distribution can be set high. Therefore, even if the permanent set
of material occurs, the fluid film intercepting function can be
performed stably.
[0096] That is to say, according to the high-friction fluid seal
10A, since the highly inclined face 1c is provided on the dust lip
1A, the effects of the above-described first invention, second
invention, and third invention can be achieved, and additionally an
effect can be achieved that the dust lip 1A is more invulnerable to
the permanent set of material while the function of dust lip of the
fluid seal having the basic configuration is maintained.
Third Embodiment
[0097] FIGS. 4(a), 4(b) and 4(c) are sectional views showing dust
lip parts of other examples of the high-friction fluid seal in
accordance with the present invention, and FIGS. 5(a) and 5(b) are
enlarged sectional views showing tip end parts of dust lips of
other examples of the high-friction fluid seal in accordance with
the present invention.
[0098] A high-friction fluid seal 10B shown in FIG. 4(a) differs
from the high-friction fluid seal 10A shown in FIGS. 3(a)-3(d) in
that a garter spring 7 is provided in the outer peripheral part of
a dust lip 1B, a small inclined face 1i directed to the tip end
part is provided on the contact side with the piston rod 13 of a
dust lip outer-side inclined face 1n so as to correspond to the
garter spring 7, and an upper inclined part 1j has a shape such as
to fittingly receive the garter spring 7.
[0099] The angle between the small inclined face 1i and the contact
surface (rod axis center) of the piston rod 13 to be sealed is
called a small inclined face angle .beta.8.
[0100] According to the high-friction fluid seal 10B provided with
the garter spring 7 on the dust lip 1B as described above, in
addition to the effect of the high-friction fluid seal 10A shown in
FIG. 3, the tightening force of the dust lip 1B can be increased,
and thereby a decrease in tightening force of the lip 1B caused by
permanent set can be compensated.
[0101] A high-friction fluid seal 10C shown in FIG. 4(b) differs
from the high-friction fluid seal 10A shown in FIGS. 3(a)-3(d) in
that a dust lip 1C has a two-stage configuration of fluid-side
inclined face provided with a stepped concave face 1k on the
inside, and a far inclined face 1p on the further inside is a
little larger than the dust lip fluid-side inclined face 1f in
FIGS. 3(a)-3d so as to correspond to the two-stage
configuration.
[0102] The angles between the stepped concave face 1k and the far
inclined face 1p and the contact surface (rod axis center) of the
piston rod 13 to be sealed are called a stepped concave face
inclination angle .beta.10 and a far inclined face inclination
angle .beta.9, respectively.
[0103] According to the high-friction fluid seal 10C in which the
dust lip 1C has the two-stage configuration of fluid-side inclined
face on the inside, the flexibility of the tip end of the lip 1C
increases, so that the transverse vibration traceability of the
dust lip 1C can be improved.
[0104] A high-friction fluid seal 10D shown in FIG. 4(c) has both
of the configurations of the high-friction fluid seal 10B shown in
FIG. 4(a) and the high-friction fluid seal 10C shown in FIG. 4(b),
and therefore can achieve the effects of both the fluid seals
synergistically.
[0105] A high-friction fluid seal 10E shown in FIG. 5(a) differs
from the high-friction fluid seal 10A shown in FIGS. 3(a)-3(d) in
that the tip end part of a dust lip 1E is not a projecting part
having a rounded cross section as a whole, and is a projecting part
1q provided with a straight line face 1n on the inside.
[0106] Also, a high-friction fluid seal 10F shown in FIG. 5(b)
differs from the high-friction fluid seal 10B shown in FIG. 4(a) in
that the tip end part of a dust lip 1F is a projecting part 1r
provided with the straight line face 1n as shown in FIG. 5(a).
[0107] Also, like the dust lip 1B shown in FIG. 4(a), the dust lip
1F has a tip end part shape having the straight line shaped small
inclined face 1i in place of the rounded face on the outer side as
well.
[0108] That is to say, in both of the above-described high-friction
fluid seals 10E and 10F, the highly inclined faces of the dust lips
1E and 1F are the straight line faces 1n, and the lip tip end part
does not have a rounded cross section as a whole. Even in such
configurations, the high-friction fluid seals 10E and 10F can
achieve the same effects as those of the high-friction fluid seals
10A and 10B.
[0109] In the case of both of the dust lips 1E and 1F as well, in
the figures, the tip end part has a minute rounded part. This
minute rounded part is inevitably produced due to the molding
process of fluid seal integrally molded using a rubber material.
Also, the minute rounded part is provided to improve the sealing
ability by making the axial contact position with the contact
surface of the lip equal around the entire circumference.
Forth Embodiment
[0110] FIG. 6 is a longitudinal sectional view showing one example
of a shock absorber using the high-friction fluid seal shown in
FIG. 3(a).
[0111] This shock absorber 20 includes a cylinder body 11, a piston
rod 14 provided with a piston, not shown, and a rod guide 15 that
is provided on the opening side of the cylinder body 11 to slidably
guide the piston rod 14. The high-friction fluid seal 10A is
tightenedly fixed between the upper end of the rod guide 15 and the
upper part of the cylinder body 11.
[0112] The cylinder body 11 includes an outer tube 11b and an inner
tube 11a that are disposed coaxially. Between the opening end part
of the inner tube 11a and the inner periphery of the opening end
part of the outer tube 11b, the rod guide 15 is provided.
[0113] On the upper surface of the rod guide 15, the oil seal 10A
is placed. By bending the upper end part of the outer tube 11b to
the inside, the outer tube 11b, the oil seal 10a, and the rod guide
15 are stakingly fixed as a unit.
[0114] In a gas chamber A formed between the inner periphery of the
outer tube 11b and the outer periphery of the inner tube 11a,
high-pressure gas is filled. A space between the inner periphery of
the inner tube 11a and the piston rod 14 is a fluid chamber L
filled with a working fluid.
[0115] The rod guide 15 is formed by press molding one metal sheet,
and includes an inside support part 15a the outer peripheral
surface of which is press fitted on the inner peripheral surface of
the inner tube 11a, an outside support part 15b the outer
peripheral surface of which is similarly press fitted on the inner
peripheral surface of the outer tube 11b, and a connecting part
15c. The connecting part 15c connects both of the support parts 15a
and 15b to each other, and the lower surface thereof comes into
contact with the opening end part of the inner tube 11a to perform
positioning of the rod guide 15.
[0116] The inside support part 15a is a guide part the inner
peripheral surface of which guides the piston rod 14, and is
configured so that the piston rod 14 is slidably guided via a
ring-shaped bush 16 having abrasion resistance, which is
press-fittingly fixed to the guide part.
[0117] The connecting part 15c is provided with a ring-shaped
projecting part 15d in the upper surface outer peripheral part
thereof. By placing the insert metal 3 of the oil seal 10A on the
upper surface of the projecting part 15d, the oil seal 10A is
positioned at a normal position with respect to the rod guide
15.
[0118] This shock absorber 20 has the above-described basic
configuration. By regulating the flow rate of working fluid filled
by a flow regulating means, not shown, the movement of the piston
is regulated, thereby fulfilling the shock absorbing function. In
addition, this shock absorber 20 has the high-friction fluid seal
10A having the above-described features. Therefore, the effect of
the high-friction fluid seal 10A can be achieved as the shock
absorber 20.
[0119] The high-friction fluid seal and the shock absorber in
accordance with the present invention are not limited to the
above-described embodiments. Various modifications and combinations
can be made in a scope described in claims and in a scope of the
embodiments, and these modifications and combinations are embraced
in the scope of right.
[0120] The working fluid includes a working oil, a liquid
containing water having properties as the working fluid for a shock
absorber, a high-molecular liquid, and a mixture of gas and
liquid.
[0121] The high-friction fluid seal in accordance with the present
invention can be used for fluid pressure equipment having the
similar problems to be solved, not limited to the shock absorber
described in the above-described examples. Also, the shock absorber
can be used for a part having the similar problems to be solved,
not limited to a suspension of a vehicle or the like.
[0122] The high-friction fluid seal in accordance with the present
invention, which is used for high-friction sealing, can be used in
industrial fields in which the solution of a problem of working
fluid leakage from a fluid lip is demanded while the fluid seal is
provided with a dust lip capable of being used for a shock absorber
for a suspension of a vehicle or the like.
[0123] The shock absorber in accordance with the present invention
is suitable to the case where the high-friction fluid seal accepts
the above-described demand.
* * * * *